Method and Apparatus for Responding to a Potential Mass Random Access Event

1. A method for responding to a mass random access event, the method comprising: monitoring, at a radio controller, a radio channel for a first period of time and determining a first indication of signals received without detecting synchronization or with detecting synchronization but failing error correction during the first period of time; responsive to determining, by the radio controller, that the first indication of signals received without detecting synchronization or with detecting synchronization but failing error correction during the first period of time is above a predetermined threshold indicative of an interference condition comprising one of an interferer and mass random access event, causing an instruction to be broadcast identifying a subset of subscriber devices, less than all subscriber devices, allowed to transmit random access requests on the radio channel; monitoring, at the radio controller, the radio channel for a second period of time and determining a second indication of signals received without detecting synchronization or with detecting synchronization but failing error correction during the second period of time; and if the second indication is an improvement over the first indication, determining, by the radio controller, that the interference condition is caused by the mass random access event.

2. The method of claim 1 , further comprising if the second indication is not an improvement over the first indication, determining, by the radio controller, that the interference condition is caused by the interferer.

3. The method of claim 1 , further comprising causing an instruction to be broadcast identifying a second subset of subscriber devices, in addition to the first subset of subscriber devices but still less than all subscriber devices, allowed to transmit random access requests on the radio channel.

4. The method of claim 3 , further comprising iteratively increasing the subsets of subscriber devices allowed to transmit random access requests on the radio channel until all subscriber devices have been allowed to transmit random access requests on the radio channel.

5. The method of claim 1 , further comprising causing an instruction to be broadcast identifying a second subset of subscriber devices that is a subset of the first subset of subscriber devices, allowed to transmit random access requests on the radio channel, such that at least one subscriber device in the first subset is no longer allowed to transmit random access requests on the radio channel.

6. The method of claim 5 , further comprising iteratively reducing a size of the subset of subscriber devices allowed to transmit random access requests on the radio channel until a number of signals received without detecting synchronization or with detecting synchronization but failing error correction during a third period of time falls below a second predetermined threshold level.

7. The method of claim 1 , wherein the radio channel is one of a control channel and a rest channel.

8. The method of claim 1 , wherein the random access requests are registration requests.

9. The method of claim 1 , wherein the message identifies a subset of subscriber devices by including a bitmask and an indication of which bits to compare between the bitmask and radio identifiers stored at each of the plurality of subscriber devices, such that a match is an indication to the receiving subscriber device that it is one of allowed to transmit random access requests on the radio channel and not allowed to transmit random access requests on the radio channel.

10. The method of claim 9 , wherein the instruction comprises a European Telecommunication Standards Institute (ETSI) Digital Mobile Radio (DMR) standard compliant C_ALOHA message.

11. The method of claim 1 , wherein the first period of time is between 0.5 and 5 seconds, inclusive.

12. The method of claim 1 , wherein the first period of time and the second period of time are substantially the same.

13. The method of claim 1 , wherein the mass random access event is caused by one of a site failure at a nearby radio site, an initial powering on of a radio site associated with the radio controller, an initial powering on of a large number of subscriber devices within a short period of time, an occurrence of an event requiring an emergency response, and a change in affiliation of a large number of subscriber devices within a short period of time.

14. The method of claim 1 , further comprising, after resolving the mass random access event and registering requesting subscriber devices, providing group-based half or full-duplex communications services to the registered subscriber devices.

15. The method of claim 1 , wherein the first and second indications are relative amounts of time during the corresponding first and second time periods during which signals were received without detecting synchronization or with detecting synchronization but failing error correction.

16. The method of claim 1 , wherein the first and second indications are a relative number of bursts during the corresponding first and second time periods for which signals were received without detecting synchronization for the burst or with detecting synchronization for the burst but failing error correction for the burst.

17. A radio controller in a radio system, the controller comprising: a transceiver; a data store; and one or more processors configured to: monitor, via the transceiver, a radio channel for a first period of time and determine a first indication of signals received without detecting synchronization or with detecting synchronization but failing error correction during the first period of time; responsive to determining that the first indication of signals received without detecting synchronization or with detecting synchronization but failing error correction during the first period of time is above a predetermined threshold indicative of an interference condition comprising one of an interferer and mass random access event, cause an instruction to be broadcast, via the transceiver, identifying a subset of subscriber devices, less than all subscriber devices, allowed to transmit random access requests on the radio channel; monitoring, via the transceiver, the radio channel for a second period of time and determining a second indication of signals received without detecting synchronization or with detecting synchronization but failing error correction during the second period of time; and if the second indication is an improvement over the first indication, determining that the interference condition is caused by the mass random access event.

18. The radio controller of claim 17 , wherein the one or more processors are further configured to, if the second indication is not an improvement over the first indication, determine that the interference condition is caused by the interferer.

19. The radio controller of claim 17 , wherein the one or more processors are further configured to cause an instruction to be broadcast, via the transceiver, identifying a second subset of subscriber devices, in addition to the first subset of subscriber devices but still less than all subscriber devices, allowed to transmit random access requests on the radio channel.

20. The radio controller of claim 17 , wherein the one or more processors are further configured to cause an instruction to be broadcast, via the transceiver, identifying a second subset of subscriber devices that is a subset of the first subset of subscriber devices, allowed to transmit random access requests on the radio channel, such that at least one subscriber device in the first subset is no longer allowed to transmit random access requests on the radio channel.